Control panels of machines such as electrical home appliances (e.g. microwave ovens, washings machines, dryers) and motor vehicles typically include multiple control knobs (control buttons and the like) to control various operational modes of such machines. A transducer will typically sense the different rotational positions of a control knob and then output electrical control signals that are indicative of the sensed rotational positions (and hence the desired operational modes of the machine as selected by the user). For instance, multiple control knobs may be disposed on a control panel of a microwave oven to control such operational modes as the heating time, heating temperature, and defrosting time. Alternately, a control panel in a motor vehicle may for instance comprise multiple control knobs for operating the air-conditioning, the radio, and the sun-roof. Furthermore, an electronic display may typically be disposed on the control panel next to the control knobs to visually display the selected operational modes of the machine that have been selected by the user. However, as the space that is available on the control panels of such machines is finite (and even more so in the context of machines with compact design aesthetics), there is a perceived need for control knobs which improve efficiency in the utilisation of control panel space on such machines without unduly compromising ease and speed of operation.